OTTAWA—Bank of Canada Gov. Stephen Poloz said earlier this year the central bank required a contingency plan for economic data because the quality of information gathered by Canada’s statistics agency could be at risk due to aging technology, according to documents reviewed by The Wall Street Journal.

Mr. Poloz’s concerns emerge in a February letter he sent to the then-head of Statistics Canada, Wayne Smith. Mr. Smith quit abruptly Friday, citing concerns about the organization’s decline and the government’s unwillingness...